RFR: 8291555: Replace stack-locking with fast-locking

[Robbin Ehn]

On Fri, 28 Oct 2022 03:32:58 GMT, Remi Forax <forax at univ-mlv.fr> wrote:

> i've some trouble to see how it can be implemented given that because of lock coarsening (+ may be OSR), the number of time a lock is held is different between the interpreted code and the compiled code.

Correct me if I'm wrong, only C2 eliminates locks and C2 only compile if there is proper structured locking.
This should mean that when we restore the eliminated locks in deopt we can inflate the recursive locks which are no longer interleaved and restructure the lock-stack accordingly.

Is there another situation than deopt where it would matter?

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PR: https://git.openjdk.org/jdk/pull/10590